I'd say it was about 6 parts potato to 1 part ground beef.

380F for about 45 minutes total. I managed to flip it about half-way without destroying it.

Edit: note that I had used quartered potatoes I had baked the night prior. So if you want to consider doing this, consider that fresh potatoes will have a much higher moisture content, and these ones were relatively dry. I would say this is a good leftover recipe, but not a good scratch recipe

Edit2: if you don't use parchment paper, you're going to have a bad time